linux-kernel - Re: [PATCH v4] sched/fair: Make per-cpu cpumasks static

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Date:   Wed, 6 Jul 2022 11:56:52 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Bing Huang <huangbing775@....com>
Cc:     rostedt@...dmis.org, dietmar.eggemann@....com, brauner@...nel.org,
        bristot@...hat.com, bsegall@...gle.com, juri.lelli@...hat.com,
        linux-kernel@...r.kernel.org, mgorman@...e.de, mingo@...hat.com,
        peterz@...radead.org
Subject: Re: [PATCH v4] sched/fair: Make per-cpu cpumasks static

On Wed, 6 Jul 2022 at 10:36, Bing Huang <huangbing775@....com> wrote:
>
> From: Bing Huang <huangbing@...inos.cn>
>
> load_balance_mask and select_idle_mask are only used in fair.c. Make

You have to rebase on tip/sched/core as select_idle_mask has been
renamed select_rq_mask

> them static and move their allocation into init_sched_fair_class().
>
> Replace kzalloc_node() with zalloc_cpumask_var_node() to get rid of the
> CONFIG_CPUMASK_OFFSTACK #ifdef and to align with per-cpu cpumask
> allocation for RT (local_cpu_mask in init_sched_rt_class()) and DL
> class (local_cpu_mask_dl in init_sched_dl_class()).
>
> Signed-off-by: Bing Huang <huangbing@...inos.cn>
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>

Beside the rebase and renaming

Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>

> ---
>
>  v1->v2:
>    move load_balance_mask and select_idle_mask allocation from
>    sched_init() to init_sched_fair_class()
>  v2->v3:
>    fixup by Dietmar Eggemann <dietmar.eggemann@....com>
>  v3->v4:
>    change the patch title and commit message
>
>  kernel/sched/core.c | 11 -----------
>  kernel/sched/fair.c | 13 +++++++++++--
>  2 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index da0bf6fe9ecd..2feff25fd905 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -9530,9 +9530,6 @@ LIST_HEAD(task_groups);
>  static struct kmem_cache *task_group_cache __read_mostly;
>  #endif
>
> -DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
> -DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
> -
>  void __init sched_init(void)
>  {
>         unsigned long ptr = 0;
> @@ -9576,14 +9573,6 @@ void __init sched_init(void)
>
>  #endif /* CONFIG_RT_GROUP_SCHED */
>         }
> -#ifdef CONFIG_CPUMASK_OFFSTACK
> -       for_each_possible_cpu(i) {
> -               per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
> -                       cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> -               per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
> -                       cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> -       }
> -#endif /* CONFIG_CPUMASK_OFFSTACK */
>
>         init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 77b2048a9326..61ae0853721e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5843,8 +5843,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  #ifdef CONFIG_SMP
>
>  /* Working cpumask for: load_balance, load_balance_newidle. */
> -DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
> -DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
> +static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
> +static DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
>
>  #ifdef CONFIG_NO_HZ_COMMON
>
> @@ -11841,6 +11841,15 @@ void show_numa_stats(struct task_struct *p, struct seq_file *m)
>  __init void init_sched_fair_class(void)
>  {
>  #ifdef CONFIG_SMP
> +       int i;
> +
> +       for_each_possible_cpu(i) {
> +               zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i),
> +                                       GFP_KERNEL, cpu_to_node(i));
> +               zalloc_cpumask_var_node(&per_cpu(select_idle_mask, i),
> +                                       GFP_KERNEL, cpu_to_node(i));
> +       }
> +
>         open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
>
>  #ifdef CONFIG_NO_HZ_COMMON
> --
> 2.25.1
>